linux-kernel - [PATCH AUTOSEL 5.10 11/12] tools/power turbostat: Fix /dev/cpu_dma

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Message-Id: <20230322200207.1997367-11-sashal@kernel.org>
Date:   Wed, 22 Mar 2023 16:02:05 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Prarit Bhargava <prarit@...hat.com>, linux-pm@...r.kernel.org,
        Len Brown <len.brown@...el.com>,
        Sasha Levin <sashal@...nel.org>, lenb@...nel.org
Subject: [PATCH AUTOSEL 5.10 11/12] tools/power turbostat: Fix /dev/cpu_dma_latency warnings

From: Prarit Bhargava <prarit@...hat.com>

[ Upstream commit 40aafc7d58d3544f152a863a0e9863014b6d5d8c ]

When running as non-root the following error is seen in turbostat:

turbostat: fopen /dev/cpu_dma_latency
: Permission denied

turbostat and the man page have information on how to avoid other
permission errors, so these can be fixed the same way.

Provide better /dev/cpu_dma_latency warnings that provide instructions on
how to avoid the error, and update the man page.

Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Cc: linux-pm@...r.kernel.org
Signed-off-by: Len Brown <len.brown@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/power/x86/turbostat/turbostat.8 | 2 ++
 tools/power/x86/turbostat/turbostat.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/power/x86/turbostat/turbostat.8 b/tools/power/x86/turbostat/turbostat.8
index f6b7e85b121ce..71e3f3a68b9df 100644
--- a/tools/power/x86/turbostat/turbostat.8
+++ b/tools/power/x86/turbostat/turbostat.8
@@ -294,6 +294,8 @@ Alternatively, non-root users can be enabled to run turbostat this way:
 
 # chmod +r /dev/cpu/*/msr
 
+# chmod +r /dev/cpu_dma_latency
+
 .B "turbostat "
 reads hardware counters, but doesn't write them.
 So it will not interfere with the OS or other programs, including
diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index ef65f7eed1ec9..d33c9d427e573 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -5004,7 +5004,7 @@ void print_dev_latency(void)
 
 	retval = read(fd, (void *)&value, sizeof(int));
 	if (retval != sizeof(int)) {
-		warn("read %s\n", path);
+		warn("read failed %s\n", path);
 		close(fd);
 		return;
 	}
-- 
2.39.2